The present invention relates to novel adhesives based on epoxy group-containing prepolymers and primary amino group-containing compounds, as well as the use of these new adhesives, especially in the production of composite films.
It is known that a great variety of so-called epoxy resins can be crosslinked with amino group-containing polyethers in order to form adhesives. It is also known, especially with reference to the production of composite films, that adhesive systems of isocyanate-containing prepolymers and polyethers with primary or secondary amino groups may be employed, specifically with the simultaneous use of solvents. Such adhesive systems, which are usually not mixed until shortly before use, generally provide usable adhesion values.
A disadvantage of these systems is the fraction of monomeric diisocyanates, for example, diphenylmethane-4,4'-diisocyanate or toluylene diisocyanate, usually present because of the random nature of the polyaddition. Because of the vapor pressure of the isocyanate, which is not negligible, especially at elevated temperatures, a number of tedious and costly occupational safety measures must be employed. Furthermore, the hardening of the systems mentioned may also be negatively influenced by atmospheric humidity and moisture in the materials, as well as residual alcoholic solvent from the printing inks used.